1. Field of the Invention
The present invent relates to a hand tool, and more particularly to a torque screwdriver which is extra provided with a forcing arm.
2. Description of the Related Art
Conventional screwdriver is a hand tool for screwing a screw element. To screw the screw element accurately, a torque screwdriver has been developed so as to set a torque force for screwing the screw element, such that the screw element will not be locked overly or inadequately. Accordingly, such a torque screwdriver is practical for precise equipment.
With reference to FIG. 1, a conventional torque screwdriver 10 contains a body 12 in which a torque mechanism 14 is mounted; and a screwing rod 16 disposed on a bottom end of the body 12 and coupling with the torque mechanism 14, such that when a force exerting on the screwing rod 16 reaches a preset torque, the torque mechanism 14 will slip off so that the screwing rod 16 cannot be rotated. In order to hold and operate the torque screwdriver securely, the body 12 has a grip bar 13 fixed on a top end thereof, and a connection shape of the body 12 and the grip bar 13 forms a T shape handle so as to form a forcing arm of the screwdriver.
Although the T shape handle serves as a forcing arm, the effect of the forcing arm is limited. In the case that a user desires to produce a large torque, the handle is rotated by the user forcefully, but such an operation is against operating requirement to torque mechanism due to the screwdriver is rotated laboriously, inappropriately and rapidly. As for a hand tool with a torque mechanism, a force exerting time to the torque hand tool must be temperate (within 4 to 6 seconds), and a force exerting speed to the torque hand tool must be appropriate. When the force exerting time is too long or too short, or the force exerting speed is inappropriate, the accuracy of the torque mechanism will be affected.
To comply with a precise torque requirement, a force rod 18 is fitted with the grip bar 13 to form a larger forcing arm, thus it is able to screw the screwing element in a large torque and with appropriate force exerting time and force exerting speed.
Nevertheless, such a conventional torque screwdriver has the following disadvantages:
For ergonomic consideration, a peripheral wall of the grip bar 13 is formed with a concave and convex surface, so the force rod 18 cannot fit with the grip bar 13 securely, and is easy to slip from the grip bar. It is thus uneasy to operate, and at the moment when the force rod 18 is slipping from the grip bar 13, the force exerting on the screwdriver changes intensely, thereby causing torque imprecision.
As the force rod 18 rotates the grip bar 13, a forcing position is not located at a center of the torque mechanism 14, i.e., an operation difference generates on the center of the torque mechanism 14, thus causing torque imprecision.
Moreover, the grip bar 13 of the T shape handle cannot be operated smoothly in a limited space.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.